1. Field of the Invention
The present invention relates generally to an electronic locating and annunciating system for a facility and, more particularly, to a system which can continuously operate to maintain a registry of the locations in the facility of individuals and equipment; and store and generate reports of a real time record of movement from location to location of individuals and equipment in the facility.
2. Description of the Prior Art
The need to maintain an up-to-date registry of the location of the personnel and equipment in a facility such as a building is oftentimes required to allow efficient operation. While the present invention is not so limited, an intelligent locator system is needed in a hospital setting, for example, to quickly locate operating personnel or emergency equipment at critical times. The ability to review accurate records of movement of personnel and equipment over time greatly enhances the ability of management to plan and maximize the utilization of resources, and allow a detailed study of events after an incident. One of the simplest methods for locating personnel within a facility involves a network of loudspeakers and phones or other response equipment. Such a network does not allow for locating equipment, only personnel. Also, broadcasting an announcement throughout the entire facility is distracting to all and requires an active response by the person being located. Furthermore, it is impractical with such network to maintain an up-to-date register for monitoring the location of personnel. U.S. Pat. Nos. 3,436,320; 3,696,384; and 3,739,329 disclose utilizing ultrasonic transmitters and receivers; however, there are disadvantages because the use of ultrasonics in these systems causes excess battery drain in the transmitters; and the ultrasonic signals pass through walls in a facility resulting in erroneous location indications.
Other prior art systems have been developed utilizing electromagnetic wave energy in the infrared frequency spectrum for the transmitters and receivers. For example, German Patent No. 32 10 002 discloses a system using infrared light emitters which transmit periodic signals for detection by a receiver that in turn energizes relays to register the presence of a person carrying the infrared emitters. No suggestion is made for preventing signal overlap between two different periodic signals transmitted by emitters carried by two different individuals. Additionally, the infrared emitters operate continuously which degrades battery longevity.
Also disclosed in U.S. Pat. No. 4,275,385 is a personnel locating system which maintains a registry of individuals by tracking their entry and exit from defined areas. Each person carries a portable transmitter, and each transmitter transmits a unique twelve bit binary code word with start, stop and parity bits employing infrared light emitting diodes. Infrared receivers are positioned to allow detection of the binary code word transmitted by the transmitter. However, the receiver can only detect the transmitted code word over a limited range, and only when the receiver is positioned so as to be in the “line of sight” of the transmitter. To overcome this problem, the receivers are positioned in doorways to rooms forming the defined area. When a person carrying a transmitter passes through the doorway, such passage is detected. The system therefore actually tracks the entrance and exit of personnel from the rooms rather than continuously maintaining the locations of the personnel. As a result, this prior art system also suffers from several inherent disadvantages. First, because a receiver only detects the transmitted signal during the brief period of time in which personnel pass through a doorway, any transmission problem occurring during this period of time results in the entry and/or exit of the personnel not be registered. Because a unique multi-bit code word as well as parity and stop/start bits must be transmitted in sequence by a portable transmitter in order to correctly identify the personnel passing through the doorway, any bit error results in an incorrect registry entry. Additionally, the number of receivers required to maintain an accurate registry of personnel increases greatly if a room contains more than one doorway allowing entrance and exit. A still further disadvantage inherent to this system occurs when two or more individuals enter through a doorway simultaneously in close proximity to one another (i.e., within the envelope of the receiver). The receiver cannot differentiate between the transmitted signals. Again, an erroneous registry indication results as no individual is registered as entering and/or exiting through the doorway. Still further, an erroneous registry indication also results when personnel pass within the envelope of the receiver, but do not pass through the doorway. For example, in a hospital setting, personnel walking along a hallway may pass within the envelope of several receivers positioned in the doorways of several rooms, but enter none of the rooms. The system would register such personnel in all of the rooms at the same time. In a hospital setting such false information is actually more detrimental than no information at all.